Field of the Invention
This invention relates generally to systems and methods for remote patient monitoring, and more particularly to an injectable physiological monitoring system for decompensation prediction of a heart failure patient.
Frequent monitoring of patients permits the patients' physician to detect worsening symptoms as they begin to occur, rather than waiting until a critical condition has been reached. As such, home monitoring of patients with chronic conditions is becoming increasingly popular in the health care industry for the array of benefits it has the potential to provide. Potential benefits of home monitoring are numerous and include: better tracking and management of chronic disease conditions, earlier detection of changes in the patient condition, and reduction of overall health care expenses associated with long term disease management. The home monitoring of a number of diverse “chronic diseases” is of interest, where such diseases include diabetes, dietary disorders such as anorexia and obesity, anxiety, depression, epilepsy respiratory diseases, AIDS and other chronic viral conditions, conditions associated with the long term use of immunosuppressant's, e.g. in transplant patients, asthma, chronic hypertension, chronic use of anticoagulants, and the like.
Of particular interest in the home monitoring sector of the health care industry is the remote monitoring of patients with heart failure (HF), also known as congestive heart failure. HF is a syndrome in which the heart is unable to efficiently pump blood to the vital organs. Most instances of HF occur because of a decreased myocardial capacity to contract (systolic dysfunction). However, HF can also result when an increased pressure-stroke-volume load is imposed on the heart, such as when the heart is unable to expand sufficiently during diastole to accommodate the ventricular volume, causing an increased pressure load (diasystolic dysfunction).
In either case, HF is characterized by diminished cardiac output and/or damming back of blood in the venous system. In HF, there is a shift in the cardiac function curve and an increase in blood volume caused in part by fluid retention by the kidneys. Indeed, many of the significant morphologic changes encountered in HF are distant from the heart and are produced by the hypoxic and congestive effects of the failing circulation upon other organs and tissues. One of the major symptoms of HF is edema, which has been defined as the excessive accumulation of interstitial fluid, either localized or generalized.
HF is the most common indication for hospitalization among adults over 65 years of age, and the rate of admission for this condition has increased progressively over the past two decades. It has been estimated that HF affects more than 3 million patients in the U.S. (O'Connell, J. B. et al., J. Heart Lung Transpl., 13(4):S107-112 (1993)).
In the conventional management of HF patents, where help is sought only in crisis, a cycle occurs where patients fail to recognize early symptoms and do not seek timely help from their care-givers, leading to emergency department admissions (Miller, P. Z., Home monitoring for congestive heart failure patients, Caring Magazine, 53-54 (August 1995)).
Recently, a prospective, randomized trial of 282 patients was conducted to assess the effect of the intervention on the rate of admission, quality of life, and cost of medical care. In this study, a nurse-directed, multi-disciplinary intervention (which consisted of comprehensive education of the patient and family, diet, social-service consultation and planning, review of medications, and intensive assessment of patient condition and follow-up) resulted in fewer readmissions than the conventional treatment group and a concomitant overall decrease in the cost of care (Rich, M. W. et al., New Engl. J. Med., 333:1190-95 (1995)).
Similarly, comprehensive discharge planning and a home follow-up program was shown to decrease the number of readmissions and total hospital charges in an elderly population (Naylor, M. et al., Amer. College Physicians, 120:999-1006 (1994)). Therefore, home monitoring is of particular interest in the HF management segment of the health care industry.
Another area in which home-monitoring is of particular interest is in the remote monitoring of a patient parameter that provides information on the titration of a drug, particularly with drugs that have a consequential effect following administration, such as insulin, anticoagulants, ACE inhibitors, beta-blockers, diuretics and the like.
Although a number of different home monitoring systems have been developed, there is continued interest in the development of new monitoring systems. Of particular interest would be the development of a system that provides for improved patient compliance, ease of use, etc. Of more particular interest would be the development of such a system that is particularly suited for use in the remote monitoring of patients suffering from HF.
Subcutaneous implantation of sensors has been achieved with an insertion and tunneling tool. The tunneling tool includes a stylet and a peel-away sheath. The tunneling tool is inserted into an incision and the stylet is withdrawn once the tunneling tool reaches a desired position. An electrode segment is inserted into the subcutaneous tunnel and the peel-away sheath is removed. In another delivery device, a pointed tip is inserted through the skin and a plunger is actuated to drive the sensor to its desired location.
In other delivery systems, an implant trocar includes a cannula for puncturing the skin and an obturator for delivering the implant. A spring element received within the cannula prevents the sensor from falling out during the implant process. Another sensor delivery device includes an injector that has a tubular body divided into two adjacent segments with a hollow interior bore. A pair of laterally adjacent tines extend longitudinally from the first segment to the distal end of the tubular body. A plunger rod has an exterior diameter just slightly larger than the interior diameter of the tubular body. With the second segment inserted beneath the skin, the push rod is advanced longitudinally through the tubular body, thereby pushing the sensor through the bore. As the implant and rod pass through the second segment, the tines are forced radially away from each other, thereby dilating or expanding the incision, and facilitating implant. The instrument is removed from the incision following implantation.
For the above and other reasons, it would be desirable to provide a non-surgical instrument and method for subcutaneous implantation of sensors and solid materials that preferably does not require an incision preparatory to instrument insertion. It would also be desirable to provide an improved home monitoring of patients with chronic conditions and improved percutaneous sensor delivery devices.